In this study, a survey on environmental radioactivity in 16 high schools located in north eastern region of Turkey (the black sea region, province of Trabzon) was carried out. Indoor air radon (Rn-222) concentrations were measured in spring and autumn 2008 seasons using LR115 solid state nuclear track detectors and gamma radioactivity levels were measured using an HPGe gamma ray detector. It was seen that mean radon activity concentrations in schools ranged from 31 to 157 Bq/m(3) for spring season and from 38 to 114 Bq/m(3) for autumn season. The mean gamma activity concentrations in located areas of schools are between 18-52, 21-59, 11-97 and 265-759 Bq/kg for Ra-226, Th-232, Cs-137 and K-40, respectively. The annual effective doses of students and staff received due to radon and locations' gamma radioactivity levels are calculated.